Set AntiAlias for BitmapDrawable to false

this is an attempt to fix #94 - documentation states that this value should be false by default - but maybe not on this particular device ..

android/src/main/java/org/ligi/passandroid/helper/BarcodeHelper.java

@@ -23,6 +23,7 @@ public class BarcodeHelper {
 
         final BitmapDrawable bitmapDrawable = new BitmapDrawable(resources, bitmap);
         bitmapDrawable.setFilterBitmap(false);
+        bitmapDrawable.setAntiAlias(false);
         return bitmapDrawable;
     }